Method of preventing double bond migration of mono-olefinic hydrocarbons in selective hydrogenation

ABSTRACT

A method of preventing double bond migration of a mono-olefin hydrocarbon during the selective hydrogenation of a polyunsaturated hydrocarbon coexisting with a mono-olefinic hydrocarbon, each of the mono-olefinic hydrocarbons and polyunsaturated hydrocarbons having at least four carbon atoms, in the presence of hydrogen, using a palladium- or nickelhydrogenation catalyst, which comprises adding carbon monoxide to the reaction system in an amount of from 1 to 50 mol. % based on said hydrogen during the initial stage of the selective hydrogenation reaction and following the initial stage, lowering the content of carbon monoxide to a range of from 0.05-1 mol. % based on the hydrogen.

llnited States Patent Komatsu et al.

[451 July 4, 1972 [72] Inventors: Youji Komatsu, Chiba; YasuhiroFurukawa, Saitama; Tallmshi Yolkomizo, Chiba,

[211 App]. No.: 109,051

[30] Foreign Application Priority Data Jan. 26, 1970 Japan ..45/6333[52] US. Cl. ..260/677 H, 260/680 [51] Int. Cl ....C07c 11/00, C07c11/12 [58] Field of Search ..260/677 H, 688

[56] References Cited UNITED STATES PATENTS 2,681,938 6/1954 Lindlar.,2s9 77 -r x 2,946,829 7/1960 Likins et al. ..260/677 H 3,075,917l/1963 Kronig et a] ..260/677 H X 3,084,023 4/1963 Andersen et a]......260/677 H X 3,325,556 6/1967 De Rosset ..260/677 H PrimaryExaminer-Tobias E. Levow Assistant ExaminerP. F. ShaverAttorney-Sughrue, Rothwell, Mion, Zinn & Macpeak [5 7] ABSTRACT A methodof preventing double bond migration of a monoolefin hydrocarbon duringthe selective hydrogenation of a polyunsaturated hydrocarbon coexistingwith a mono-olefinic hydrocarbon, each of the mono-olefinic hydrocarbonsand polyunsaturated hydrocarbons having at least four carbon atoms, inthe presence of hydrogen, using a palladiumor nickel-hydrogenationcatalyst, which comprises adding carbon monoxide to the reaction Systemin an amount of from 1 to 50 mol. based on said hydrogen during theinitial stage of the selective hydrogenation reaction and following theinitial stage, lowering the content of carbon monoxide to a range offrom 005-! mol. based on the hydrogen.

.s w imsrNePre qsa a METHOD OF PREVENTING DOUBLE BOND MIGRATION OFMONO-OLEFINIC HYDROCARBONS llN SELECTIVE HYDROGENATION BACKGROUND OF THEINVENTION 1. Field of the Invention The present invention relates to amethod of preventing the double bond migration of mono-olefinichydrocarbons during the selective hydrogenation of polyunsaturatedhydrocarbons of polyolefinic and/or acetylenic types coexisting withsaid mono-olefinic hydrocarbons, each of the mono-olefinic hydrocarbonsand the polyunsaturated hydrocarbons having at least four carbon atoms.

2. Description of the Prior Art It is generally known that apolyunsaturated hydrocarbon of the polyolefinic and/or acetylenic typehaving at least four carbon atoms, coexisting with a mono-olefmichydrocarbon having at least four carbon atoms, may be hydrogenated inthe presence of a hydrogenation catalyst, such as palladium, platinum ornickel, by hydrogen to selectively convert said polyunsaturatedhydrocarbons into the corresponding monoolefinic hydrocarbons. Such aprocess is hereinafter referred to as selective hydrogenation." Forexample, it is widely known that a butene fraction containing C-diolefins and/or C,-acetylenes may be selectively hydrogenated in thepresence of a palladium, platinum or nickel catalyst by hydrogen toconvert said C -diolefins and/or C -acetylenes into the correspondingbutenes, with little loss of butenes, thereby obtaining the butenefraction substantially free from said Q-diolefins and C,-acetylenes.

However, the conventional hydrogenation catalysts, such as palladium,platinum and nickel, used for such selective hydrogenation processespossess the disadvantage of promoting double bond migration in additionto the desired hydrogenation of the unsaturated bonds. Accordingly,conventionally practiced selective hydrogenation employing suchcatalysts are inevitably accompanied by double bond migration ofmono-olefinic hydrocarbons.

For example, in the selective hydrogenation of the butene fractioncontaining l-butene, C -diolefins (e.g., l,3butadiene, methyl allene)and/or C -acetylenes e,g., dimethyl acetylene, ethyl acetylene, vinylacetylene) in the conventional process, both the selective hydrogenationreaction of C -diolefins and/or C acetylenes into butenes and the doublebond migration of l-butene into Z-butene take place simultaneously underthe same reaction condition. As a result, the greater part of thel-butene is lost. This problem becomes very serious when it is desiredto selectively hydrogenate C,- diolefins and/or C -acetylenes coexistingwith l-butene to obtain a pure l-butene or a fraction rich in l-butene,free from C -diolefins and C -acetylenes. l-butene and l-butenerichfractions are extremely useful as chemical feed materials for theproduction of poly-l-butene, l-butene copolymer, etc.

Meanwhile, it has been known in the selective hydrogenation of ethylenecontaining acetylene in the presence of a hydrogenation catalyst tocharge carbon monoxide or a sulfur compound (for example, hydrogensulfide, mercaptans, carbon disulfide) into the reaction system;however, the carbon monoxide is not used to prevent the double bondmigration of a mono-olefinic hydrocarbon, but is employed to increasethe selectivity of the hydrogenation catalyst, i.e. for the purpose offacilitating the hydrogenation of acetylene selectively into ethylenewithout excessive hydrogenation of ethylene into ethane.

A process employing severe hydrogenation conditions, ie at a temperatureof 93.3-.260 C. under pressure of l75-245 kg/cm G, has been proposed inconnection with preparing a mono-olefinic feedstock containing a minorproportion of polyolefin for oxoaldehyde synthesis. Under these severeconditions, skeletal isomerization of mono-olefinic hydrocarbons takesplace in addition to the double bond migration.

There has also been described a process for the hydrogenation ofacetylenes coexisting with diand mono-olefins,

acetylenes and diolefins coexisting with mono-olefins over a coppercatalyst containing a minute portion of an activating metal. However,when carbon monoxide is used to depress the hydrogenation of1,3-butadiene, isomerization of l-butene to Z-butene occurs.

Thus, it has been long desired in this art to develop a method ofpreventing the double bond migration of monoolefinic hydrocarbonseffectively during the selective hydrogenation of polyunsaturatedhydrocarbons coexisting with mono-olefinic hydrocarbons.

We have described in our copending application, Ser. No. 828,186, howcarbon monoxide (but not sulfur compounds) has the particular propertyof preventing double bond migration in selective hydrogenation of theaforesaid hydrocarbon mixtures, using known catalysts, and have claimeda method of preventing the double bond migration in which thehydrogenation is carried out in the presence of 1-50 mol. of carbonmonoxide, based on the hydrogen, through the entire reaction.

SUMMARY OF THE INVENTION It is therefore the basic object of the presentinvention to provide a method for preventing the double bond migrationof mono-olefinic hydrocarbons during the selective hydrogenation ofpolyunsaturated hydrocarbons coexisting with monoolefinic hydrocarbons,each of the mono-olefinic hydrocarbons and polyunsaturated hydrocarbonshaving at least four carbon atoms, in the presence of hydrogen using acopper-free palladium or nickel hydrogenation catalyst.

Another object of the present invention is to provide a method ofeffectively preventing the double bond migration of mono-olefinichydrocarbons during the selective hydrogenation of polyunsaturatedhydrocarbons by the use of a small amount of carbon monoxide.

Still another object of the present invention is to provide a processfor the selective hydrogenation of polyunsaturated hydrocarbonscontaining mono-olefinic hydrocarbons, each of said polyunsaturatedhydrocarbons and mono-olefinic hydrocarbons having at least four carbonatoms, in the absence of the usual accompanying double bond migration.

Still another object of the present invention is to provide a method ofinhibiting only the isomerization (double bond migration) activity ofconventional hydrogenation catalysts being employed for the selectivehydrogenation of polyunsaturated hydrocarbons coexisting withmono-olefinic hydrocarbons, each of said polyunsaturated hydrocarbonsand monoolefinic hydrocarbons having at least four carbon atoms.

These and other objects of the present invention will become moreapparent from the following description thereof.

Accordingly, we have now found that double bond migration ofmono-olefinic hydrocarbons can also be effectively prevented during theselective hydrogenation of polyunsaturated hydrocarbons coexisting withsaid mono-olefinic hydrocarbons, each of the mono-olefinic andpolyunsaturated hydrocarbons having at least four carbon atoms, in thepresence of hydrogen and a copper-free palladium or nickel hydrogenationcatalyst, by carrying out said selective hydrogenation in the presenceof 1-50 mol. preferably 5-30 mol. of carbon monoxide based on thehydrogen during the initial stage of the reaction and thereafter in thepresence of 0.05-l mol. of carbon monoxide, based on the hydrogen.

DETAILED DESCRIPTION OF THE INVENTION According to the process of thisinvention, the polyunsaturated hydrocarbons coexisting with themono-olefinic hydrocarbons, each of which hydrocarbons having at leastfour carbon atoms, are selectively hydrogenated in the presence ofhydrogen and 1-50 mo]. during the initial stage of the reaction andthereafter 005-] mol. of carbon monoxide, respectively based on thehydrogen, by the use of a Irunw: rvnn copper-free palladium or nickelcatalyst. As a result, said polyunsaturated hydrocarbons are selectivelyhydrogenated and thus eliminated, and the double bond migration of saidmono-olefinic hydrocarbons is effectively prevented. For instance, it ispossible to effectively prevent the double bond migration, not only inthe selective hydrogenation of l,3-butadiene and/or otherpolyunsaturated hydrocarbons coexisting with butenes, but also in theselective hydrogenation of other C or higher polyunsaturatedhydrocarbons coexisting with higher mono-olefinic hydrocarbons, by theprocess of the present invention.

A hydrocarbon feed utilized in the selective hydrogenation of thepresent invention comprises a mixture of mono-olefinic hydrocarbon and apolyunsaturated hydrocarbon, each having at least four carbon atoms.Practically speaking, the hydrocarbon feed may contain hydrocarbonshaving up to 16 carbon atoms. The said polyunsaturated hydrocarbons arepolyolefinic hydrocarbons (e.g., diolefins, triolefins and the like)and/or acetylenic hydrocarbons (e.g., alkynes, alkenynes). The contentof the polyunsaturated hydrocarbons in the hydrocarbon feed ispreferably less than about 50 mol. Feeds containing greater amounts ofpolyunsaturated hydrocarbons may, however, be employed within the scopeof the invention. In addition, the hydrocarbon feed may containparaffinic hydrocarbons, such as n-butane, pentane, hexane, etc.; inertgases such as hydrogen, nitrogen, etc; and occasionally a small amountof C polyunsaturated hydrocarbon, such as methyl acetylene and allene.

The hydrogen to be used in this invention may be either pure hydrogen orhydrogen-containing gases, such as natural gas, reformer off-gas, etc.

if the hydrocarbon feed already contains hydrogen, the rest of thehydrogen being required for the selective hydrogenation of thisinvention may be supplied from an external source. The amount ofhydrogen employed in the present invention will vary depending upon thecontents of the polyunsaturated hydrocarbon in the hydrocarbon feed. Itis necessary to use more than the stoichiometric amount of hydrogenneeded for hydrogenating the polyunsaturated hydrocarbons intocorresponding mono-olefinic hydrocarbons. in general, l-20,000 moles ofhydrogen per total mole of polyunsaturated hydrocarbons may be employedfor the selective hydrogenation.

The hydrogenation catalyst to be used in the present inven tion is acopper-free hydrogenation catalyst containing palladium or nickel.Suitable hydrogenation catalysts are palladium or nickel metals, or thesulfides or oxides of these metals, or such metals or compoundssupported on known carriers, such as alumina, silica-alumina, magnesia,titania, diatomaceous earth, etc., by conventional treatment. Preferablecatalysts are palladium supported on carrier (Pd cont. 0.005-3 weight ornickel on a supported carrier (Ni cont. 1-40 weight To carry out theselective hydrogenation readily without the double bond migration of themono-olefmic hydrocarbons, the hydrogen in the reaction system mustcontain l-50 mol, preferably 5-30 mol. of carbon monoxide, based on thehydrogen present, during the initial stage of the reaction. In theinitial stage of the reaction, an amount of carbon monoxide of less than1 mol. based on the hydrogen is not desirable, for double bond migrationwill take place along with the selective hydrogenation. When the contentof carbon monoxide is also more than 50 mol. other disadvantages appear,such as prolongation of the reaction period for the selectivehydrogenation of the polyunsaturated hydrocarbon. However, the doublebond migration is still prevented.

The carbon monoxide may be introduced to the reaction system in anymanner as long as hydrogen is also present. in practical operation, itis convenient to previously mix the carbon monoxide with hydrogen in aspecific ratio and then to bring the resultant carbon monoxide-hydrogenmixture into contact with the hydrocarbon feed.

In accordance with the present invention, the content of carbon monoxideis thereafter (after the initial stage) lowered to a later (followingthe initial stage) range, i.e. 0.05-l mol. (based on the hydrogenpresent) at once, stepwise or continuously. Said later content of carbonmonoxide in an amount of less than 0.05 mol. is not desirable, sincedouble bond migration will also take place along with the selectivehydrogenation. If the later content of carbon monoxide is more than 1mol. the double bond migration does not take place in the selectivehydrogenation. However, said process wherein the amount of carbonmonoxide is more than 1 mol. is shown in our copending application asmentioned above. Naturally, it is no harm to the process of the presentinvention that the later content of carbon monoxide remains in theinitial range, i.e. l-50 mol. But economically, the smallest amount ofcarbon monoxide possible should be employed in the reaction since carbonmonoxide is relatively expensive.

In the process of the present invention, the content of carbon monoxideis lowered from the initial range, i.e. 1-50 mol. to the later range,i.e. 0.05-1 mol. after the hydrogenation catalyst has been treated witha requisite amount of carbon monoxide under a high content (1-50 mol. ofcarbon monoxide during the initial stage of hydrogenation reaction. Thecontent of carbon monoxide may usually be lowered to the later range of005-1 mol. after the total amount of carbon monoxide added to thereaction system comes to at least 0.05 moles per gram of thehydrogenation catalyst. The content of carbon monoxide can be lowered tothe later range after the total amount of carbon monoxide comes topreferably at least 0.l20 moles, most preferably at least 0.2l0 moles,per gram of the catalyst.

Industrially, new carbon monoxide is not added to the reaction systemduring the decrease of carbon monoxide content from the initial rangel50 mol. to the later range (0.05-l mol. On approaching of the carbonmonoxide content to the later range, new carbon monoxide begins to beintroduced into the reaction system along with hydrogen. In therestarting ofthe hydrogenation reaction following the interruption ofthe reaction, the content of carbon monoxide is enough in the laterrange (0.05-l mol. provided that the catalyst is treated in the initialrange with l-5O mol. of carbon monoxide at least once.

The selective hydrogenation of the present invention is preferablycarried out at a temperature of 20-250 C. under the pressure of aboutatmospheric to 50 kg/cm. Under such a relatively mild reactioncondition, skeletal isomerization of the mono-olefinic hydrocarbons willnot occur in any substantial amount during the selective hydrogenation.Whenever the content of carbon monoxide is lowered, it is preferable toemploy the milder reaction conditions, e.g., to lower the temperature ofhydrogenation reaction as shown in the examples. Said milder reactionconditions are chosen to prevent excessive hydrogenation. In this case,the double bond migration can be effectively prevented even thoughhydrogenation temperature is or is not lowered. The hydrocarbon feed isintroduced as either an upflow or downflow to a reactor packed with thehydrogenation catalyst at a liquid hourly space velocity (L.H.S.V.) of0. and is selectively hydrogenated therein. Although it is convenient tocontact the hydrocarbon feed with the hydrogenation catalyst in a fixedbed, if necessary or desired a moving or fluidized bed may be employed.The selective hydrogenation may be carried out in either a batch,semicontinuous or continuous operation. It is also possible to introducea sulfur compound, such as hydrogen sulfide, mercaptan or carbondisulfide together with carbon monoxide to the reaction system for thepurpose of avoiding excessive hydrogenation in the process of thisinvention. However, the sulfur compound itself has no ability to preventthe double bond migration as mentioned above.

According to the process of this invention, it has now become possibleto effectively prevent double bond migration in mono-olefinichydrocarbons which has always accompanied conventional selectivehydrogenation of mixtures of mono-olefinic and polyunsaturatedhydrocarbons having at least four carbon atoms. The process of thisinvention therefore has wide industrial applications not only as aprocess for selective hydrogenation in the absence of double bondmigration but also as a process for the production of a particularhydrocarbon which may be altered during conventional selectivehydrogenation by double bond migration.

The present invention is particularly useful in carrying out theselective hydrogenation of butenes containing Q-diolefins and/or C-acetylenes without lowering the l-butene content, and also in obtainingl-butene, or a fraction rich in l-butene, from l-butene mixtures with C-diolefins and/or C -acetylenes by selective hydrogenation. However, thefield of the application of the present invention is not limited only tothese specific examples.

A better understanding of the present invention will be attained fromthe following examples, which are merely intended to be illustrative andnot [imitative of the present invention.

EXAMPLE 1 The hydrocarbon feed employed was a butene-containing feedhaving the composition shown in Table I. Said butene feed is a raffinateextracted from a C fraction produced by naphtha steam cracking.

The hydrogenation catalyst employed was a commercial palladium catalyst(PGC-C" produced by Englehard Industries, Ltd.) containing 0.1 by weightof palladium supported on alumina.

A vertically disposed reactor of 50 mm inner diameter was packed with200 m1 of the palladium catalyst. Into the reactor there werecontinuously introduced the butene feed at the rate of 600 ml/hr(L.H.S.V. 3.0) and hydrogen containing 25 mol. carbon monoxide at therate of 60 liters (N.T.P.)/hr, at a temperature of 90 C. and pressure of25 kg/cm to effect the selective hydrogenation. The hydrogenated productthus obtained was analyzed by gas chromatography.

The composition of the hydrogenated product (except hydrogen and carbonmonoxide) which is obtained after 2 hours from the start of selectivehydrogenation, is given in the column headed Product A" in Table 1.

After 4 days from the start of the reaction, the content of carbonmonoxide, based on the amount of hydrogen present, was changed from 25mol. to 0.7 mol. At the same time, the temperature of hydrogenation waslowered from 90 to 60 ,C. to prevent excessive hydrogenation.

The composition of the product thus obtained is described under ProductB in Table 1.

As is apparent from Table l, the content of l-butene in Product B is thesame as that in Product A. This clearly proves that the double bondmigration during the selective hydrogenation is effectively preventedwhen the content of carbon monoxide based on the hydrogen is changedfrom 25 mol. 70 to 0.7 mol. after the initial stage of the reaction.

COMPARATIVE EXAMPLE 1 The selective hydrogenation was carried out usingthe same feed, catalyst and reaction conditions as those used in Example1 except that hydrogen free from carbon monoxide was utilized. Thecomposition of the butene feed and the compositions of the hydrogenationproducts, Product A" obtained after 2 hours from the start of thereaction, and Product B obtained after 4 days, are shown in Table 2.

TABLE 2 As apparent from Table 2, almost all of the l-butene undergoesdouble bond migration and is converted to Z-butene during selectivehydrogenation when carbon monoxide is not present in the reactionsystem.

EXAMPLE 2 The procedure of Example 1 was repeated except that thehydrocarbon feed employed was a C -fraction having the composition shownin Table 3, which was produced by naphtha steam cracking. The reactionwas carried out at a temperature of 80 C. under a pressure of 25 kglcmand the rate of hydrogen containing 5 mol. carbon monoxide was 500liters (N.T.P. )/hr.

The composition of the product obtained after 2 hours from the start ofthe'reaction is shown under Product C in Table 3.

After 15 days from the start of the reaction, the content of carbonmonoxide based on hydrogen was changed from 5 mol.

to 0.5 mol. and the reaction temperature was lowered from 80 to 60 C. toprevent excessive hydrogenation.

The composition of product thus obtained is also given under Product Din Table 3.

TABLE 3 Feed Product Composition Composition (mol.

(mol. Product C Product D Isobutene7.l 7.1 7.2' n-Butane6.0 6.1 6.1lsobutene24.l 25.3 25.0 l-Butene13.8 23.0 23.3 2-Butene8.0 38.5 38.4l,3-Butadiene39.2 (94 p.p.m.) (88 p.p.m.) Vinyl acetyleneLS (0 p.p.m.)(0 p.p.m

EXAMPLE 3 The procedure of Example 1 was repeated except that thereaction was carried out at a temperature of C. under a pressure of 15kglcm and the rate of hydrogen containing 5 mol. carbon monoxide was 50liters (N.T.P.)/hr. A nickelcontaining hydrogenation catalyst containing1.0 by weight of nickel supported on alumina was used in place ofpalladium-alumina catalyst.

The composition of the product obtained after two hours from the startof the reaction is shown under Product E" in Table 4.

After 30 days from the start of the reaction, the content of carbonmonoxide was changed from mol. to 0.5 mol. and the temperature ofhydrogenation was lowered from 100 to 70 C, to prevent excessivehydrogenation.

The composition of the product thus obtained is given under Product F inTable 4.

TABLE 4 Feed Composition (mol.

Product Composition (mol. Product E Product D EXAMPLE 4 The procedure ofExample I was employed except that the reaction was carried out at atemperature of 100 C. under a pressure of kglcm The composition of theproduct obtained after 2 hours from the start of the reaction is givenunder Product G" in Table 5.

After 30 days from the start of the reaction, the content of carbonmonoxide based on hydrogen present was changed from 25 mol. to 2.0 mol.and the reaction temperature was lowered from 90 to 80 C. to preventexcessive hydrogenation.

After 60 days from the start of the reaction, the content of carbonmonoxide was further changed from 2.0 mol. to 0.5 mol. and the reactiontemperature was lowered from 80 to 60 C.

The compositions of the former and the latter product are given underProduct H and Product K, respectively, in Table 5': I

TABLE 5 Having now described the present invention with'particularity,it is readily apparent that various changes and modifications may bemade without departing from the scope thereof.

What is claimed is:

l. A process for the selective hydrogenation of at least one member,having at least four carbon atoms in the molecule, selected from thegroup consisting of a polyolefm, an alkyne, and alkenyne, and mixturesthereof in a hydrocarbon mixture containing at least one mono-olefinhaving at least four carbon atoms in the molecule, which comprisescontacting said hydrocarbon mixture with a copper-free hydrogenationcatalyst com rising a member selected from the hgroup consistmg of pallarum and nickel under selective ydrogenation conditions in the presenceof hydrogen and carbon monoxide of 1-50 mol. based on the hydrogen,during the initial stage of the reaction and thereafter lowering thecontent of carbon monoxide to a range of 0.05-l mol. based on thehydrogen, said process preventing double bond migration of themonoolefin.

2. The process of claim 1, wherein the carbon monoxide is present in anamount of from 5 to 30 mol. based on the hydrogen during the initialstage of the reaction.

3. The process of claim 1, wherein the content of carbon monoxide islowered after the total amount of carbon monoxide added into thereaction system comes to at least 0.05 moles per gram of thehydrogenation catalyst.

4. The process of claim 1, wherein the content of carbon monoxide islowered after the total amount of carbon monoxide added into thereaction system comes to at least 0.1-20 moles per gram of thehydrogenation catalyst.

5. The process of claim 1, wherein the content of carbon monoxide islowered after the total amount of carbon monoxide added into thereaction system comes to at least 0.2-10 moles per gram of thehydrogenation catalyst.

6. The process of claim 1, wherein the hydrogenation is carried out at atemperature of from 20 to 250 C.

7. The process of claim 1, wherein the hydrogenation is carried outunder a pressure of from atmospheric to 50 kglcm 8. The process of claim1, wherein the hydrocarbon mixture is a mixture of compounds having from4 to 16 carbon atoms in the molecule.

9. The process of claim 8, wherein the hydrocarbon mixture is a Cfraction.

10. The process of claim 8, wherein the hydrocarbon mixture is a Cfraction.

11. The process of claim 1, wherein the hydrocarbon mixture containsparaffinic hydrocarbons.

12. The process of claim 1, wherein the catalyst is supported on acarrier.

13. The process of claim 12, wherein the catalyst is palladium supportedon alumina.

14. The process of claim 12, wherein the catalyst is nickel supported onalumina.

15. The process of claim 1, wherein the amount of palladium catalystpresent ranges from 0.0053.0% by weight.

16. The process of claim 1, wherein the amount of nickel catalystpresent ranges from l-40% by weight.

17. The process of claim 1, wherein the amount of hydrogen per totalmole of polyunsaturated hydrocarbons ranges from l20,000 moles.

18; The process of claim 1, wherein the liquid hourly space velocity ofthe hydrocarbon feed ranges from 0.1 to 40.0.

2. The process of claim 1, wherein the carbon monoxide is present in anamount of from 5 to 30 mol. % based on the hydrogen during the initialstage of the reaction.
 3. The process of claim 1, wherein the content ofcarbon monoxide is lowered after the total amount of carbon monoxideadded into the reaction system comes to at least 0.05 moles per gram ofthe hydrogenation catalyst.
 4. The process of claim 1, wherein thecontent of carbon monoxide is lowered after the total amount of carbonmonoxide added into the reaction system comes to at least 0.1-20 molesper gram of the hydrogenation catalyst.
 5. The process of claim 1,wherein the content of carbon monoxide is lowered after the total amountof carbon monoxide added into the reaction system comes to at least0.2-10 moles per gram of the hydrogenation catalyst.
 6. The process ofclaim 1, wherein the hydrogenation is carried out at a temperature offrom 20* to 250* C.
 7. The process of claim 1, wherein the hydrogenationis carried out under a pressure of from atmospheric to 50 kg/cm2.
 8. Theprocess of claim 1, wherein the hydrocarbon mixture is a mixture ofcompounds having from 4 to 16 carbon atoms in the molecule.
 9. Theprocess of claim 8, wherein the hydrocarbon mixture is a C4 fraction.10. The process of claim 8, wherein the hydrocarbon mixture is a C5fraction.
 11. The process of claim 1, wherein the hydrocarbon mixturecontains paraffinic hydrocarbons.
 12. The process of claim 1, whereinthe catalyst is supported on a carrier.
 13. The process of claim 12,wherein the catalyst is palladium supported on alumina.
 14. The processof claim 12, wherein the catalyst is nickel supported on alumina. 15.The process of claim 1, wherein the amount of palladium catalyst presentranges from 0.005-3.0% by weight.
 16. The process of claim 1, whereinthe amount of nickel catalyst present ranges from 1-40% by weight. 17.The process of claim 1, wherein the amount of hydrogen per total mole ofpolyunsaturated hydrocarbons ranges from 1-20,000 moles.
 18. The processof claim 1, wherein the liquid hourly space velocity of the hydrocarbonfeed ranges from 0.1 to 40.0.